a. Field of the Invention
The present invention relates generally to orthotic foot appliances, and more particularly to an improved orthotic device for treatment of gait cycle disorders which frequently develop in patients suffering from diabetes, rheumatoid arthritis and certain other conditions.
b. Background
Relevant to the background of the present invention, there will now be a discussion of the following: i) the main components or parts of the human leg and foot; ii) the proper gait cycle which a person goes through in a normal walking motion; and iii) the abnormal gait cycle which develops from diabetes, rheumatoid arthritis or other conditions which impair proper transfer of weight onto the forefoot when walking, and which is corrected by the present invention.
a) The Main Components or Parts of the Human Leg and Foot
With reference to FIGS. 1-3, there is shown a typical human foot 10, and the lower part 12 of the leg 14. The two lower bones of the leg 14 are the tibia 16 and the fibula 18. Below the tibia 16 and fibula 18, there is the talus 20 (i.e., the xe2x80x9cankle bonexe2x80x9d). Positioned below and rearwardly of the talus 20 is the calcaneus 22 (i.e., the xe2x80x9cheel bonexe2x80x9d). Positioned moderately below and forward of the talus 20 are the navicular 24 and the cuboid 26. Extending forwardly from the navicular 24 are the three cuneiform bones 28. Extending forwardly from the cuneiform bones 28 and from the cuboid 26 are the five metatarsals 30. Forwardly of the metatarsals 30 are the phalanges 32 which make up the five toes 34.
The movement of the talus 20 relative to the tibia 16 and fibula 18 is such that it enables the entire foot to be articulated upwardly and downwardly (in the motion of raising or lowering the forward part of the foot). However, the talus 20 is connected to the tibia 16 and fibula 18 in such a way that when the entire leg 14 is rotated about its vertical axis (i.e., the axis extending the length of the leg), the talus 20 rotates with the leg 14.
With regard to the relationship of the talus 20 to the calcaneus 22, these move relative to one another about what is called the xe2x80x9csubtalar jointxe2x80x9d indicated at 36. The subtalar joint 36 can be described generally as a hinge joint about which the talus 20 and calcaneus 22 articulate relative to one another. The hinge axis extends upwardly and forwardly at an angle of about 42xc2x0 from the horizontal, and also slants forwardly and inwardly at a moderate angle (e.g., about 16xc2x0 from a straightforward direction). There is also the midtarsal joint 38, which is in reality composed of two separate joints, the talo-navicular and the calcaneal-cuboid.
b) Gate Cycle of a Normal Foot
During the normal walking motion, the hip (i.e., the pelvis) moves on a transverse plane. Also, the femur (i.e., the leg bone between the knee joint and the hip) and the tibia rotate about an axis parallel to the length of the person""s leg. This rotation of the leg about its vertical axis is interdependent with the pronating and supinating of the foot during the gait cycle. There is also flexion and extension of the knee and the ankle joint.
At the beginning of the normal gait cycle the heel of the forwardly positioned leg strikes the ground, after which the forward part of the foot rotates downwardly into ground engagement. The leg then continues through its walking motion to extend rearwardly and the person pushes off from the ball of the foot as the other leg comes into ground engagement.
The phases that make up the gait cycle can be seen in FIG. 4. When the leg is swung forwardly and makes initial ground contact, at the moment of ground contact the leg is rotated moderately to the outside (i.e., the knee of the leg is at a more outward position away from the centerline of the body) so that the foot is more toward the supinated position. However, as the person moves further through the gait cycle toward the 25% position, the leg rotates about its vertical axis in an inside direction so that the subtalar joint is pronating. The effect of this is to rotate the heel of the foot so that the point of pressure or contact moves forwardly from an outside rear heel location (shown at 52 in FIG. 5) towards the location indicated at 54 in FIG. 5. This pronating of the subtalar joint 36 produces a degree of relaxation of the midtarsal joint 38 and subsequent relaxation of the other stabilization mechanisms within the arch of the foot, which reduces the potential shock that would otherwise be imparted to the foot by the forward part of the foot making ground contact.
With further movement from the 25% to the 75% position, the leg rotates in an opposite direction (i.e., to the outside so that the midtarsal joint 38 becomes supinated at the 75% location of FIG. 4. This locks the midtarsal joint 38 so that the person is then able to operate his foot as a rigid lever so as to rise up onto the ball of the foot and push off as the other leg moves into ground contact at a more forward location.
With reference again to FIG. 5, it will be seen that the initial pressure at ground contact is at 52 and moves laterally across the heel to the location at 54. Thereafter, the pressure center moves rather quickly along the broken line indicated at 56 toward the ball of the foot. As the person pushes off from the ball of the foot and then to some extent from the toes of the foot, the center of pressure moves to the location at 58.
c) Abnormal Gait Cycle of the Foot of a Person Suffering From Diabetes or Rheumatoid Arthritis
FIG. 6 shows a side view of the foot 60 of a person suffering from diabetes or rheumatoid arthritis, this view being essentially identical to the corresponding view of the normal foot that is shown in FIG. 2.
A common problem is that people suffering from these conditions tend to avoid using their toes when they walk. Typically, this is because of the pain that exists in the areas of the ball of the foot 62 (under the metatarsal heads) and the toes 64. Furthermore, in the case of a diabetic condition, the poor circulation caused by this disease frequently leads to the development of painful sores in those areas which are subjected to repeated pressure or friction, again especially under the ball of the foot and toes.
Because of the discomfort, a person suffering from rheumatoid arthritis or diabetes learns more or less unconsciously to minimize the pressure on the forward portion of the foot when walking, resulting in the abnormal gait cycle that is illustrated in FIG. 7. These views show the person""s right foot and lower leg, and correspond to the views shown in FIG. 4. As can be seen, during the initial phases the action of the person""s foot is essentially the same as in a normal gait cycle. However, when the person""s foot moves from the 50% point towards the 75% point in the cycle, as is shown in the fourth view, the weight begins to be transferred forwardly and generally towards the area of the first metatarsal head, as indicated above with reference to FIG. 5. If rheumatoid arthritis is present in the forefoot area, this causes the person significant pain or discomfort, which tends to increase in intensity as the weight moves forwardly towards the toes. Consequently, the person seeks to reduce the pain by avoiding transfer of weight forwardly beyond the ball of the foot, with the result that the normal xe2x80x9ctoe-offxe2x80x9d action does not occur; instead, the foot is lifted away from the ground more or less horizontally at the end of the gait cycle, as is shown in the right-hand view of FIG. 7.
Over time, this action becomes automatic, so that the person develops a shuffling gait in which the feet simply flatten out after heel strike and then lift off again in a horizontal orientation. This abnormal gait cycle is extremely inefficient, and frequently leads to development of other problems in the person""s feet and legs. Moreover, the constant pressure on the ball of the foot at the end of the abortive gait cycle tends to xe2x80x9csqueezexe2x80x9d the blood out of the comparatively thin layer of tissue that exists under the bones in this part of the foot, eventually leading to development of sores and serious tissue damage.
Although the shuffling gait cycle and lack of toe-off described above are commonly associated with rheumatoid arthritis and diabetes, it will be understood that there are other conditions affecting the leg and/or foot that can lead to similar problems. For example, a condition of functional hallux limitus (often resulting from arthritis in or at the base of the large toe, from an elevated first ray, or from some other structural malformity) can precipitate foot and gait problems very much like those described above.
There have been previous attempts to treat these problems by devising a special shoe having a rocker bottom, in an effort to move the person""s foot into more of a toe-off position before the end of the gait cycle. However, this solution is excessively expensive and the special shoes are uncomfortable and difficult to use, especially for elderly patients. However, if the condition is left untreated additional foot and leg problems can develop, and in some cases the damage to the foot may progress to the point where a partial or full amputation is required.
Accordingly, there exists a need for a device which facilitates proper toe-off by the foot at the end of the gait cycle, so as to ensure proper foot motion and avoid development of an improper shuffling gait, particularly in individuals suffering from rheumatoid arthritis, diabetes, functional hallux limitus or other conditions that prevent the normal transfer of weight onto the forefoot portion of the foot. Furthermore, there exists a need for such a device that induces proper toe-off at the end of the gait cycle without causing pain in toes and forefoot portions of a foot of a person suffering from rheumatoid arthritis, diabetes or similar condition. Still further, there exists a need for such a device that can be used with a conventional shoe, both for convenience and to minimize the cost to the user, and also to permit the user to employ a single device or pair of devices with several different shoes. Still further, there exists a need for such a device that can be shaped to meet the contours and specific requirements of the feet of individual users. Still further, there exists a need for such a device that can be manufactured in a quick, efficient and economical manner, and that is durable and long lasting and will sustain extended use without collapsing, breaking, or otherwise undergoing significant deterioration.
The present invention has solved the problems cited above, and is an orthotic insert that is removably insertable in a shoe for providing enhanced orientation of a foot at the toe-off position of the gait cycle.
Broadly, the insert comprises a substantially rigid cap member for engaging a plantar surface of a person""s foot, the cap member having a rearward portion for extending beneath an arch and rearfoot portion of a person""s foot, a forward portion for extending to a position at least proximal the metatarsal head portion of the foot, and a ridge portion extending downwardly from the cap member proximate the junction between the forward and rearward portions thereof for engaging an upper surface of an insole of the shoe so as to form a pivot point that causes the cap member to tilt forwardly in response to a shift in weight from the rearfoot portion to the forefoot portion of the foot, so that as weight shifts forwardly on the foot as the orthotic insert tilts forwardly in the shoe so as to orientate the foot at increased forward angle at the toe-off position of the gait cycle.
A ridge portion may extend transversally across the bottom of the rigid cap member, and may be formed integrally with the cap member. The ridge portion may extend at an angle that is substantially parallel to an angle of a row of metatarsal heads of the foot. The transverse ridge portion may be positioned proximate to and slightly rearwardly of the metatarsal head area of the foot, so that the cap member tilts forwardly in response to weight being transferred forwardly towards the metatarsal head area.
The rearward portion of the rigid cap member may include a curved arch portion following an arch portion of the foot, while the forward portion of the cap member may include a metatarsal flange portion for extending forwardly beneath the metatarsal head area of the foot along the transverse plane of the foot. The ridge portion may be formed substantially level with the flange portion of the cap member, at a location a spaced distance rearwardly from a position of the metatarsal head area of the foot, so that at this location the ridge portion extends a predetermined vertical height below the arch portion of the cap member.
The rigid cap member of the insert may have a forward edge for being positioned proximate the metatarsal head area of the foot. The forward edge of the cap member may extend at an angle substantially parallel to the angle of the row of metatarsal heads of the foot. The insert may further comprise a forefoot extension mounted to the flange portion and extending forwardly therefrom for transmitting downward forces from the forefoot portion of the foot to the flange portion of the cap member. The forefoot extension may comprise a layer of resiliently cushioning material mounted to the flange portion of the cap member.
The rigid cap member may be formed of at least one layer of fiber-resin material. The insert may further comprise a resilient, cushioning blank member mounted atop the rigid cap member for engaging a plantar surface of the foot.